This disclosure concerns an invention relating generally to methods and apparata for fluid dispensation, i.e., the dispensation of liquids and flowing powders, particulates, or other solids. The invention relates more particularly to methods and apparata which are particularly suitable for use in automatic and semi-automatic container fillers for filling containers with a desired amount of fluid product.
The three most common types of fluid filling schemes are volumetric filling, time-metered filling, and weight-metered filling (also referred to as gravimetric filling). All are commonly implemented in semi-automatic or automatic filling systems wherein empty containers are carried by conveyors or other transport mechanisms to filling positions. Once the containers reach the filling positions, they are stopped, filled to the desired degree by filling heads (e.g., nozzles or other dispensing apparata), and then released upon completion of the fill. In other instances, no container transport mechanisms are utilized and the containers are simply placed by hand at the filling station, filled, and then removed by hand after filling.
In volumetric filling (also known as volume-metered filling), a set volume of fluid is dispensed into a container: a chamber is set to a desired volume, the chamber is filled with fluid, and the contents of the chamber are then dispensed into a container. The chamber is generally provided by a cylinder which is emptied by a piston. Volumetric filling is subject to the disadvantages that filling accuracy is limited by the accuracy of the control of the chamber volume, and filling speed is limited by the time necessary for refilling the chamber. Volumetric filling is also unsuitable where one wishes to fill a container with a desired weight of fluid: variations in fluid density will lead to variations in the weight of the fluid dispensed from the chamber and result in different weights being dispensed into different containers; viscous fluids may stick to the dispensing apparatus and result in incomplete dispensation; and so forth.
In time-metered filling (also known as time-metered volumetric filling), fluid is dispensed from a nozzle having a known volumetric flow rate for a set amount of time sufficient to fill the containers with a set volume of fluid. Time-metered filling is advantageous in terms of productivity insofar as one may reduce filling time per container to any desired level so long as the appropriate volumetric flow rate is obtainable. However, time-metered filling is subject to inaccuracy unless a constant flow rate is precisely maintained, and this is particularly difficult to attain where flow rates are high. Additionally, time-metered filling is subject to the same disadvantages as volumetric filling in that variations in fluid density will result in different weights of fluid being dispensed to different containers, even if the volume of the dispensed fluid remains relatively constant from container to container.
Weight-metered (gravimetric) filling utilizes a weight sensor which monitors the amount of fluid received by a container. The weight sensor provides feedback to the dispensing apparatus, which halts dispensation when a desired weight of fluid is received. Weight-metered filling can be more accurate than volume-metered and time-metered filling, but it unfortunately has several significant disadvantages. First, the weight sensors and feedback apparata are quite costly if any reasonable degree of accuracy is required. Second, the filling time per container tends to be significantly longer owing to the weight feedback; sensitive weight sensors need time to xe2x80x9csettlexe2x80x9d prior to giving accurate weight readings, and additionally slower filling rates must often be used since the flow must be cut off precisely at or slightly before the time the desired weight is reached, or overshoot will result in an overweight container with product xe2x80x9cgive-awayxe2x80x9d.
Regardless of whatever filling methodology is used, it has long been recognized that the versatility of filling units (i.e., the devices that perform the filling function) are significantly enhanced if the filling units are repositionable between different filling stations (i.e., the conveyors or other areas at which filling is to be performed), or to cleaning and maintenance areas. Apart from enhancing the ease of repairs and cleaning of filling units, this allows a single filling unit to be used at a variety of different filling stations, and additionally different filling units may be interchangeably used at the same filling station. As an example, mobile semiautomatic volumetric filling units have been well known for many years. As an example, the NEUMO Model SAF filling unit (Cherry Burrell, Delavan, Wis.) provided a piston/cylinder volumetric pump on a wheeled base, with the cylinder being supplied with fluid from a product hose (which could be connected to a product supply tank or the like) and in turn supplying a filling head. A foot pedal was supplied so that depression of the foot pedal would actuate the volumetric pump. Thus, a user could situate a container at a filling station, wheel the filling unit over to the filling station so that the filling head rested over the container, and the pedal could then be depressed to fill the container.
U.S. Pat. No. 4,445,548 to Neumann describes a mobile filling unit wherein a filling head is provided on a wheeled base. The filling head is supplied with fluid via a conduit which may be connected and disconnected from a fluid product source. The wheeled base is provided with retractable legs so that the filling unit may be fixed in position once it is wheeled to a desired filling station, with the filling head positioned over filling positions to which empty containers are indexed for filling. Metered filling is accomplished by means of monitoring the level of fluid received in the filled containers. As fluid is dispensed from the filling head, a collar surrounding the filling head floats or rides on the surface of the dispensed fluid, and the collar will eventually trigger a limit switch on the filling unit when the fluid fills the container to a desired level. Once filling is completed, an empty container is situated under the filling head and the operator recommences the filling process. Filling of subsequent containers is made somewhat easier by supplying them to the filling station on a conveyor, and additionally the filling head extends or retracts after each filling cycle so that the filling unit can more easily dispense fluids into containers in both lanes of a dual-lane conveyor.
Such semiautomatic filling systems, while useful, are not well suited for high production speeds and significant output of filled containers. In these situations, automatic filling systems are preferable, with containers being supplied by conveyors, indexers, or other container transport equipment (which will be collectively referred to as xe2x80x9cconveyorsxe2x80x9d throughout the remainder of this document). Automatic filling systems are necessarily more complex because the extent of filling of the containers must be measured, either gravimetrically, volumetrically, or by other methods, and the filling units which effect filling must communicate with the conveyors to synchronize the filling operation with the container supply. Examples of prior automatic filling systems follow.
U.S. Pat. No. 4,398,577 to Sauer illustrates a mobile volumetric filling unit with twin filling heads. The mobile filling unit may be wheeled to various filling stations (such as conveyor lines) and positioned so that the filling heads are situated over filling positions to which empty containers are indexed. Fluid is volumetrically dispensed from each filling head, and dispensation is synchronized with the filling station/conveyor by a chain and sprocket arrangement. The filling unit may be disconnected from the filling station by removal of the chain, allowing the filling unit to be removed from the filling station and wheeled to cleaning areas, or to other filling stations for reconnection.
U.S. Pat. No. 5,505,233 to Roberts et al. describes a mobile gravimetric filling unit with multiple filling heads which may be wheeled between a filling station (such as a conveyor) at which weight sensors are located, and cleaning or other areas. Empty containers are indexed on the conveyor to rest over weight sensors. Fluid is then dispensed from the filling heads into the containers, and once each container reaches a desired weight, dispensation ceases. The filling unit communicates with the weight sensors by use of pneumatic lines. In commercial versions of this and similar filling systems, disconnectable pneumatic lines are used between the filling unit(s) and the filling station so that one filling unit can be disconnected from the pneumatic lines and replaced with another filling unit. Alternatively, a pair of filling units may be simultaneously pneumatically connected to the filling station, with only one filling unit being positioned adjacent to (and being used at) the filling station at a time. When it is desired to have the other filling unit perform filling, the first filling unit is wheeled away from the filling station and the other is wheeled in to replace it. The filling units can both remain connected to the filling station throughout this process, though disconnects are provided on their pneumatic lines so that either filling unit can be disconnected from the filling station if desired.
To better illustrate filling systems of this nature, it is useful to review a filling system owned by the Fuller O""Brien Company (South San Francisco, Calif., USA) for use in paint filling operations, and which was displayed at the Oct. 21-23, 1992 Paint and Coatings Federation Trade Show in Chicago, Ill. This filling system included two mobile filling units, each having a vertical mast bearing a wheel at its bottom, with the mast supporting a bank of four filling heads. The mast of each mobile filling unit had an arm which extended horizontally to pivotally connect to a conveyor. Thus, each filling unit could be wheeled in an arc along the floor up to a filling position at the conveyor, at which point its arm rested parallel and adjacent to the conveyor, and each of its filling heads rested over a corresponding gravimetric weight sensor on the conveyor. From this position, each filling unit could also be wheeled away from the conveyor, e.g., to a cleaning area where its filling heads were situated away from the filling position. The pivot points for the two arms of the filling units were spaced apart on the same side of the conveyor such that the mobile filling units could interchangeably swing to the same filling position over the weight sensors. Electrical communication lines ran from the weight sensors to a control box associated with the conveyor, and pneumatic lines then extended from the control box to the filling heads of the filling units. Thus, the filling heads communicated with the weight sensors via an electrical-to-pneumatic interface, and dispensed fluid into containers on the weight sensors in accordance with the weight sensed thereon. The pneumatic lines were removably connected to the filling heads by quick-disconnect fittings. An electrical line also ran from the control box to terminate at a limit switch on each arm so that when a filling unit was moved to the filling position, the switch on its arm contacted the conveyor, thereby allowing the controls to detect when the filling unit was at the filling position or the cleaning area. A filling unit at the filling position could be latched to the conveyor to prevent its filling heads from swinging out of alignment with the weight sensors at the filling position.
In operation, a first one of the filling units was latched to the conveyor at the filling position, and it was connected to a fluid product source (e.g., a tank). Each of its filling heads were situated over a corresponding weight sensor on the conveyor to allow gravimetric filling of containers situated thereon. The second filling unit was situated away from the filling position at a cleaning area, and was connected to a source of flushing fluid so that its filling head could be flushed out, with the flushing fluid being received by a vat. Once cleaning of the first filling unit was desired, it was disconnected from the product source, unlatched from the conveyor, and wheeled along an arc defined by its arm to a location distant from the filling position. The source of flushing fluid was then disconnected from the second filling unit and connected to the first filling unit for flushing. The second filling unit was wheeled on the floor along an arc defined by its arm into the filling position, at which point its filling heads were situated over the load cells on the conveyor. It was then connected to the fluid product source so it could perform gravimetric filling of containers on the load cells.
One disadvantage of the foregoing filling systems is their requirement that a communications connection be established between the filling unit and the filling station in order to allow filling to be synchronized with the container supply: Sauer requires the chain of the filling unit be connected to the filling station, and the filling systems of the Roberts et al. type require that the pneumatic lines of the filling units be connected to the filling station and its weight sensors. These connections may take time to establish and verify; consider, for example, that the chain of Sauer must be attached to the sprocket at a correct location, or else the synchronization between the filling unit and conveyor will be improperly timed. Similarly, since several pneumatic lines are required between a Roberts et al. -type filling unit and filling station for proper communication between the filling unit and weight sensors, one must verify that the pneumatic lines are properly connected to avoid ill-timed fluid dispensation. Additionally, the mechanical and pneumatic connections of Sauer and Roberts et al., which essentially have the nature of xe2x80x9cumbilicalsxe2x80x9d which extend between the filling unit and filling station, can provide a tripping hazard, are subject to damage during transport of the filling units or when activities occur in the filling environment, and/or can be fouled (e.g., by product spills). Damage and/or fouling can make connection between the filling units and filling stations difficult (or impossible), or it may interfere with proper synchronization. Further, the mechanical and pneumatic connections can remain connected when the filling units are knocked to some degree out of alignment with their filling stations, thereby allowing the filling units to continue dispensing fluid even when the fluid is only partially being received within the containers (and the remainder is being dispensed onto the filling station).
The inventor and his colleagues have considered various options for filling systems that might eliminate the need for a communications connection between the filling unit and filling station, whereby a filling unit may be quickly placed adjacent a filling station with its filling head(s) over the container filling positions without the need to establish a physical communications connection between the filling unit and filling station. As an example, a filling unit and filling station might communicate via a wireless interface (e.g., by radio frequency communications) so that filling/synchronization messages may be communicated therebetween. However, such electronic communications are subject to noise interference from other electronics in the filling system""s environment, and additionally the components needed to enable such communications are prohibitively expensive (at the time this document was filed as a patent application). The same is true of sonic/ultrasonic communications, which are even more subject to noise interference.
Another option is to have the filling unit communicate with the filling station by optical communications, as by transmission of an infrared filling/synchronization signal. Optical communications have the advantage that they are highly directional, and thus the filling unit must be properly situated with respect to the filling station during dispensation in order to enable the communications (and thus in order to enable dispensation of fluid). In other words, an operator need not worry about the filling unit dispensing fluid when the filling unit is misaligned with respect to the filling station in such a manner that it dispenses fluid out of, or only partially within, the containers to be filled. However, while optical communications components have reasonable cost, they are particularly subject to fouling by spilled product: once spilled product distorts or obscures the light beam which provides the filling signal, the system becomes inoperative or malfunctions.
An additional problem with all of the foregoing modes of communication is that they generally require electronics for operation, and it is often desirable to avoid electronics in filling environments wherein flammable materials are used. To illustrate, many filling units are flushed or cleaned using volatile solvents, and electronics can cause ignition of the solvents or their vapors. This is why pneumatic actuation of (and communication between) filling units and filling stations is commonly used. There are known and commonly used methodologies and equipment for explosion-proofing electronics in filling systems, but it would be useful to avoid the cost and inconvenience of these measures.
Thus, to summarize, it would be useful to have a filling system wherein the filling unit (or units) is repositionable with respect to the filling station, and wherein filling/synchronization signals are communicated between the filling unit(s) and filling station without the need for a communications connection therebetween.
The invention, which is defined by the claims set forth at the end of this document, is directed to methods and apparata which at least partially alleviate the aforementioned problems. A basic understanding of some of the preferred features of the invention can be attained from a review of the following brief summary of the invention, with more details being provided elsewhere in this document.
A preferred version of the invention involves a fluid product filling system having a filling unit which is repositionable with respect to a filling station. The filling unit includes a filling head and a dispensing switch. The filling head may be switched between two states, a filling state wherein fluid product is dispensed from the filling head, and a nonflow state wherein fluid product dispensation is ceased. The dispensing switch, which may be a contact or proximity switch, may be actuated to change the filling head between these states.
The filling station has a filling position at which a container may be placed for filling with fluid product. A container fill sensor, e.g., a weight sensor such as a load cell or digital scale, is preferably provided on the filling station at the filling position so that it may detect the degree to which a container situated at the filling position is filled with fluid product. A movable switching member is also preferably provided on the filling station, and it communicates with the container fill sensor and moves to different positions in accordance with the degree to which a container at the filling position is filled. For example, the switching member may be provided by a rod driven by a pneumatic cylinder.
The filling unit is repositionable with respect to the filling station so that the filling unit may be situated adjacent the filling station with its filling head situated over the filling position, or may be moved to allow the filling unit to rest at other locations. When the filling unit is resting adjacent the filling station with its filling head situated over the filling position (i.e., when it is in the ready-to-fill position), the switching member and dispensing switch are adjacently situated between the filling unit and filling station so that the switching member may actuate the dispensing switch. No connection between the switching member and dispensing switch is made, and instead the switching member simply extends to push or otherwise act on the dispensing switch to actuate the filling head. To illustrate, where the switching member is a rod driven by a cylinder (or is some other form of linear or pivoting actuator), the switching member may act as a finger which actuates the dispensing switch. Where the dispensing switch is a proximity switch rather than a contact switch (for example, a magnetic proximity switch), the switching member need only approach the dispensing switch to a sufficient degree that the dispensing switch is actuated, and no contact between the switching member and dispensing switch is necessary.
Thus, when the container fill sensor then detects that filling is to occur (or is to cease), the switching member is actuated, which in turn actuates the dispensing switch to change the filling head between its filling state and its nonflow state in accordance with the filling detected by the container fill sensor. When the filling unit is moved away from the filling station such that its filling head is no longer situated over the filling position, the switching member cannot reach or actuate the dispensing switch and the filling unit becomes inoperable (with the filling head preferably being normally close, but opened by the dispensing switch, so that it will automatically be closed once the filling unit is moved away from the filling station).
The foregoing arrangement has exceptionally fast shut-down and start-up time because a filling unit only needs to be put in the ready-to-fill position, with its filling head situated over the filling position, in order to establish communications between the filling unit and the filling station. No connections between the filling unit and filling station are required. This lack of connections also reduces maintenance and increases safety, since there need not be any pneumatic or electric lines extending between the filling unit and filling station. Such lines can cause tripping or which can easily be damaged by traffic adjacent to the filling operations, either while they are connected or when they are disconnected and trailing from the filling unit and/or filling station. It is also notable that when the invention is used in lieu of filling systems wherein pneumatic communications conduits are connected between the filling unit and filling system, the invention provides more accurate filling. This is because pneumatic communications signals are subject to degradation and delay, as they may only travel at the speed of sound, and a portion of the signal is lost owing to expansion of flexible pneumatic conduits (particularly in longer conduits). Where pneumatics are used in the invention, such degradation and delay is greatly reduced because the length of any pneumatic circuits allowing communication between the filling unit and filling station are interrupted by the switching member and dispensing switch. For example, as compared to prior filling systems wherein a pneumatic communication line extended from the filling unit to a container fill sensor at the filling station, the invention allows the lengths of the pneumatic lines on the filling unit side and the filling station side to be reduced by as much as one-half.
Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings.